Re: runs poorly

Posted by Steve@Advance on November 04, 2022 at 21:25:49 from (99.190.215.237):

In Reply to: runs poorly posted by jimmyzie on November 04, 2022 at 16:03:03:

A couple things come to mind...

Just to say you did it, check the ignition system. Check the points
condition, gap, distributor shaft for side play, the centrifugal advance
function, wires and plugs. Check the spark quality at the plug end of
each wire. It needs at least 1/4 inch spark to ground to run properly.

Also, have you checked the valve clearance? Any chance the compression is
down? The carb can only work as well as the rest of the engine. It's a
pain to set the valves, the gas tank has to come off, but it's necessary
to keep everything in tune. The compression needs to be at least 90 PSI
and somewhat equal between the cylinders.

Back to the fuel system. In order for the old carb to have been rusted
and corroded internally, there had to have been water in the fuel! Unless
the tank has been removed and cleaned, there is still a water problem.
And while the tank is off, see above!

There is a drain plug in the bottom of the carb bowl. with the engine
off, fuel valve open, get a clean glass, remove the plug and catch the
flow. First, it should have a full flow of fuel, the flow should continue
as a stream, not slow to a drip or stop. Look at what was caught. if you
run non ethanol gas, any water will be on the bottom of the glass. So
will any sediment, trash, or rust. If you have a dirty, rust flaking, or
water contaminated tank, the same will be in the carb, and will be an
ongoing problem until it is addressed. Nothing more frustrating! If the
tank is flaking rust, the easiest solution is to buy a new replacement.

If the carb is contaminated, it is easy enough to open it up and clean
it. Usually the gasket can be saved and reused.

As for adjusting the carb, which needs to be done last, after everything
is right and all problems corrected, then it can be successfully
adjusted. You say it refuses to idle below 1000 RPM, that is a clue there
may be a compression problem. The engine should easily idle well at 400-
500 RPM, and it must be idling that slow for the idle adjustment to be
effective.

The idle mixture adjustment, (the small screw up above the throttle
plate), is really an air bleed adjustment. Turning it in richens the mix,
backing it out leans the mix. It has very limited overall effect. So,
with the engine up to temp, idle adjusted down to 400 RPM, turn the screw
out until the idle gets rough, then back in until it idles best.

The main adjust, (the large knob type screw on top of the bowl cover),
adjusts the main jet flow. Start with the screw about 2 turns off the
(gently) fully screwed in position. Let the engine idle down to slow
idle, then suddenly open the throttle and listen to the response. When
properly adjusted the engine will take sudden throttle without
hesitation. Keep repeating the test, turning the screw in 1/4 turn until
it stumbles on acceleration, then back it out 1/8 turn at a time until it
takes throttle responsively. A single puff of black smoke is desirable.

Hope this helps, let us know!

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